Large scale production of materials by fermentation is often limited by the costs associated with regulating gene expression. Often the strategies employed require expensive sugar derivatives or other small molecules to trigger protein production leading to desired products.
Promoters are nucleic acid molecules which comprise the 5′ regulatory elements that play an integral part in the overall expression of genes in living cells. Isolated promoters that function in host cells or organisms are useful for controlling the expression of operably linked transgenes and thereby modifying host organism or cell phenotypes through the methods of genetic engineering.
NtcA is the primary controller of the nitrogen regulon of cyanobacteria, having a DNA-binding sequence (GTAN8TAC). Depending upon placement relative to the promoter and the transcription start position, NtcA binding can either activate or repress transcription (reviewed in Herrero et al. 2001 and Muro-Pastor et al. 2005). NtcA-mediated control of transcription is influenced by the nitrogen to-carbon ratio, with 2-oxoglutarate functioning as the effector molecule. Emlyn-Jones et al. (2003) disclosed the use of the nitrite reductase promoter for mutS expression, allowing control of the mutation frequency of Synechococcus elongatus PCC 7942 by varying the nitrogen source.
The ribulose-1,5-bisphosphate carboxylase oxygenase (RuBisCo) promoter from cyanobacteria is thought to be one of the strongest known promoters, since RuBisCo is one of the proteins expressed in highest abundance in the biosphere.